Hi,
I just heared, when we use powerful dimmer (Maybe PWM) like in mega structures to control light intensity etc, it causes distortion in AC and distortions can produce unexpected heat in cables and sometime fires. I saw a video and found that to remove the distortion, they used a bigger capacitor like 6 inch in diameter. Where they use the capacitor? I searched some equivalent circuit but found nothing exactly.

More than likely it was a common, but large, power factor correction capacitor connected across the main power lines.

Besides adjusting the power factor up those types of capacitors typically have very low ESR ratings which make them very effective as harmonics traps and HF snubber devices too.

I use several smaller ones, ~ 2 uF 600 VAC ,around my home and shop electrical system just for that purpose of knocking out HF noise on the AC line sides which in some of the things I experiment with probably gets pretty wild.

Hi
I cannot see videos in the internet. I saw a engineering program in National Geography channel where they were describing many basic engineering techniques behind a Burj Al Arab, mega structures. And they were talking about light dimmer technology and a big capacitor. I have posted a YouTube link thinking that I found that video by guessing just from its thumbnail picture.

More than likely it was a common, but large, power factor correction capacitor connected across the main power lines.

Besides adjusting the power factor up those types of capacitors typically have very low ESR ratings which make them very effective as harmonics traps and HF snubber devices too.

I use several smaller ones, ~ 2 uF 600 VAC ,around my home and shop electrical system just for that purpose of knocking out HF noise on the AC line sides which in some of the things I experiment with probably gets pretty wild.

Click to expand...

Hi,
Small 2uF 600V capacitors like used in single phase AC motors? How you connect them in mains, any circuitry?

Hi,
I just heared, when we use powerful dimmer (Maybe PWM) like in mega structures to control light intensity etc, it causes distortion in AC and distortions can produce unexpected heat in cables and sometime fires. I saw a video and found that to remove the distortion, they used a bigger capacitor like 6 inch in diameter. Where they use the capacitor? I searched some equivalent circuit but found nothing exactly.

Click to expand...

You'll need to find out whether its PWM, or something else.

PWM usually implies the standard rectifier/reservoir like in a typical SMPSU. The most common PFC front end is a flyback boost converter interposed between the rectifier and reservoir. It works at a much higher frequency than mains and takes pulses of current from the rough DC waveform that are proportional to its amplitude. On some ATX PSUs they just stick a dirty great iron-cored choke in series with the mains input.

On a triac dimmer - a PFC capacitor will do little more than take the edges off the switched current waveform.